Thin film fuel cell electrolyte and method for making

ABSTRACT

An electrolyte has a core and at least one projection extending from the core. The core is supported on a substrate, and the at least one projection is separated from the substrate.

FIELD OF THE INVENTION

The invention is in the thin film fuel cell field. The inventionparticularly concerns thin film electrolytes, thin film structures, thinfilm fuel cells, electronic devices incorporating thin film fuel cells,and methods for making thin film electrolytes and fuel cells.

BACKGROUND OF THE INVENTION

A fuel cell is an electrochemical device that directly combines a fueland an oxidant, such as hydrogen and oxygen, to produce electricity andexhaust, such as water. It has an anode or fuel electrode and a cathodeor air electrode separated by an electrolyte. Hydrogen is oxidized toprotons on the anode with an accompanying release of electrons. At thecathode, molecular oxygen reacts to form oxygen ions, consumingelectrons in the process. Electrons flow from the anode to the cathodethrough an external load, and the circuit is completed by ionic currenttransport through the electrolyte. Hydrogen fuel cells do not emit toxicgasses. They operate quietly and have a potential efficiency of up toabout 80 percent.

A particular class of fuel cells is thin film cells that include a solidelectrolyte layer. This type of fuel cell is particularly well suitedfor applications such as small and microelectronics devices. Generally,the potential power output of a fuel cell varies nearly directly withthe useful interface area between the electrolyte and anode and betweenthe electrolyte and cathode. To provide increased output from thin filmcells, longer and wider anode, cathode, and electrolyte layers have beenprovided. Enlarging these layers has required an enlarged footprint forthe cells. This is undesirable in microelectronics devices.

Additional problems are known with solid oxide thin film fuel cells. Forexample, the cells typically require a relatively high operatingtemperature in the 700-1000° C. range. These high temperatures can leadto delamination problems in thin film cells. In particular, thermalcycling to and from these operating temperatures can cause substantialthermal expansion and contraction of the various fuel cell layers.Because the layers are made of different materials having differentcoefficients of thermal expansion, they may expand and contract bydifferent amounts. This can cause the layers to come apart from oneanother.

Solutions to some of these problems have been proposed. For example, ithas been proposed to construct cells using anode, cathode, andelectrolyte layers having similar coefficients of thermal expansion.This can be difficult, however, since closely matching coefficients ofthermal expansion do not necessarily correlate to increased cellperformance.

SUMMARY OF THE INVENTION

According to the invention, an electrolyte for use with a thin film fuelcell comprises an electrolyte core that is supported on a substrate. Atleast one electrolyte projection extends from the core and is suspendedover the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is side view of an embodiment of an electrolyte of the invention;

FIG. 2 is a top view of the electrolyte of FIG. 1;

FIG. 3 is a top view of an embodiment of an electrolyte arrangement ofthe invention;

FIG. 4 is side view of an embodiment of a fuel cell of the inventionthat includes the electrolyte of FIG. 1;

FIG. 5 is side view of an additional embodiment of a fuel cell of theinvention that includes the electrolyte of FIG. 1;

FIG. 6 is a side view of an additional embodiment of an electrolyte ofthe invention;

FIG. 7 is side view of an embodiment of a fuel cell of the inventionthat includes the electrolyte of FIG. 6;

FIG. 8 is a side view of an embodiment of a fuel cell assembly of theinvention;

FIG. 9 is a side view of an additional embodiment of a fuel cellassembly of the invention;

FIG. 10 is a side view of an additional embodiment of a fuel cellassembly of the invention;

FIG. 11 is a side view of an additional embodiment of a fuel cellassembly of the invention;

FIG. 12 is a flow chart illustrating an embodiment of a method of theinvention;

FIGS. 13(a)-13(g) illustrate various stages of formation of anembodiment of a fuel cell of the invention;

FIGS. 14(a)-14(k) illustrate various stages of formation of anadditional embodiment of a fuel cell of the invention; and

FIGS. 15(a)-(b) illustrate various stages of formation of an embodimentof an electrolyte structure of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to thin film fuel cells, electrolytesfor thin film fuel cells, electronic devices that include a thin filmfuel cell, and methods for making electrolytes and thin film fuel cells.The present invention provides many advantages. For example, the shapeof thin film electrolytes achieved through practice of the presentinvention allows for good mechanical attachment of the layers of a thinfilm fuel cell, and therefore for improved resistance to delamination.Additionally, increased interlayer surface area provides for relativelyhigh reaction rates, and tortuous structures can be formed that increasethe turbulence in the flow field. These and other advantages of theinvention will be better appreciated through consideration of thedetailed description of exemplary invention embodiments described hereinand shown in the drawings. Turning now to the drawings, FIGS. 1 and 2illustrate a thin film electrolyte embodiment of the invention generallyat 10. The electrolyte 10 has a substantially vertical core 12 supportedon a substrate 14. The substrate 14 may be conductor that isconductively linked to the core 12, or may be a dielectric. The core 12has a three-dimensional generally rectangular shape, although theinvention could be practiced using cores having a variety of othershapes, with examples including but not limited to circular, elliptical,polygonal, and the like. A plurality of projections 16 is integrallyconnected to the core 12 and is suspended over the substrate 14. As usedherein the term “integrally connected” is intended to broadly refer tobeing part of the same whole and continuous with.

The projections 16 extend outwards from a generally planar core firstside 20 and an opposing generally planar second side 22. The projections16 are thus supported over the substrate 14, and have gaps 18 definedbetween them. The projections 16 are shaped in the general form of athree-dimensional rectangle although other shapes can be considered, andare generally wider and thinner than the core 12 to maximize their topand bottom surface areas.

Thin film electrolytes of the invention such as the exemplaryelectrolyte 10 offer several advantages. For example, the projections 16provide increased surface area for contact with anodes and cathodes.Furthermore, the projections 16 are beneficial in providing for strongmechanical attachment to an anode and cathode, and to thereby reducedelamination problems. Also, these structures can be arranged in anon-linear configuration to form tortuous paths for the flow of the fueland oxidants to increase the likelihood of gas/surface interactions.

It will be appreciated that the thin film electrolyte may be made ofsuitable materials as are generally known in the art. By way of example,if the electrolyte 10 is for use in a solid oxide fuel cell, it may bemade of materials such as, by way of example and not limitation, aceramic such as yttria stabilized zirconia, samaria doped ceria,gadolinia doped ceria, lanthanum strontium gallium maganite, and thelike. It will be appreciated that the electrolyte 10 is not limited touse with solid oxide fuel cells, and may be useful in many additionaltypes of cells in which it may be desired to form the electrolyte 10 ofa different material. By way of example, the electrolyte 10 (and/orelectrolyte support structure) may be useful in any of a protonicceramic, proton exchange membrane, molten carbonate, alkalineelectrolyte or phosphoric acid fuel cells. The core 12 may have a widthillustrated as dimension A in FIG. 2 of between about 1 and about 1000microns. A preferred width is between about 1 and about 250 microns.Each of the projections 16 has a width B as illustrated by FIG. 2 ofbetween about 0.25 and about 1500 microns. The core 12 may have a heightC as illustrated by FIG. 1 as small as about 0.25 micron and as large asabout 500 microns. Each of the projections 16 preferably has a heightillustrated as D in FIG. 1 of between about 1 micron and about 50microns.

Particular dimensions of the core 12, projections 16, and the substrate14, including length, may vary depending on a particular application. Itmay be desirable, for example, to provide an electrolyte 10 shaped andsized to maximize interface area, to maximize reduction of delamination,to form gas channels, and the like. In the exemplary cases of increasedsurface area and reduced delamination, it may be preferred to usesmaller electrolytes 10 with an increased density per unit area ascompared to gas channel applications.

With reference to FIG. 2 by way of example, the dimension A may be about1 micron or less for an electrolyte structure embodiment of theinvention useful to increase surface area and reduce delamination, thedimension B being between about 0.25 and about 5 microns for theseapplications, and the dimension D (FIG. 1) between about 1 micron andabout 2 microns. In the exemplary case of forming gas channels, it maybe preferred to use larger electrolytes to form larger channels andthereby reduce the restriction on the air and/or fuel flows. For gaschannel electrolyte applications, by way of example, the dimension A ofFIG. 2 may be about 250 microns, the dimension B about 500 microns, andthe dimension D (FIG. 1) about 50 microns.

In addition, other core 12 and projection 16 shapes may be useful forthese applications. For example, unconnected square, rectangular, orcircular structures may be useful to increase surface area, reducedelamination and increase the turbulence of gas flow past thestructures. Indeed, in an additional exemplary embodiment of theinvention, a plurality of individual electrolyte structures are providedin a non-linear configuration in order to increase the turbulence of gasflowing past fuel cells that are formed on the electrolyte structures.FIG. 3 is a top plan view illustrating a plurality of generallyhexagon-shaped electrolyte cores 12 and projections 16 configured on asubstrate 14 in a non-linear arrangement to increase the turbulence ofgas flow. It will be appreciated that although common element numbersfor describing the cores, projections, and substrate of FIG. 3 have beenused with reference to FIGS. 1-2, the projections and cores of FIG. 3have a different shape than those of FIGS. 1-2. Those knowledgeable inthe art will further appreciate that many other shapes and arrangementswill be useful for maximizing useful surface area and increasing flowturbulence.

Advantages of electrolytes of the invention will be better appreciatedwhen considering fuel cells embodiments of the present invention. FIG. 4illustrates a fuel cell shown generally at 30 that includes theexemplary electrolyte 10 of FIGS. 1 and 2. An anode 32 is attached tothe first side 20 of the electrolyte and to the plurality of projections16 that extend from that side. A cathode 34 is attached to the opposingsecond side 22 and to the plurality of projections 16 extending fromthat side. The anode 32 and cathode 34 from the same cell are preferablyseparated from one another, although the anode 32 and cathode 34 ofadjacent cells can be connected for stacking purposes. As is generallyknown in the art, a current collector 35 may be provided to communicatecurrent between the anode 32 and cathode 34 and to an electric load 37such as a microprocessor or other electronics or microelectronicsdevice. The current collectors 35 shown here are only by way ofillustration and many different designs can be considered. Those skilledin the art will also understand that the current collector 35 should notimpede the performance of the electrodes, which may be accomplished forinstance, by utilizing a porous current collector 35.

It will be appreciated that the anode 32 and cathode 34 enjoy arelatively strong mechanical attachment to the electrolyte 10 ascompared to generally flat, layered, electrolytes of the prior art,because of the configuration of the electrolyte 10. In addition, arelatively high surface interface area is achieved between theelectrolyte 10 and the anode 32 and cathode 34 while maintaining arelatively small footprint. This provides for relatively high currentoutput-due to the large effective surface area.

FIG. 5 illustrates an additional invention embodiment in the form of theexemplary fuel cell 40. The cell 40 is similar to the cell 30 exceptthat the anode 42 and cathode 44 are formed in a thin layer to generallymatch the surface of the electrolyte 10. The thickness of the anode 42and cathode 44 may be as small as about 0.5 micron or less. This may beadvantageous to provide a larger reactive surface area than theconfiguration of FIG. 4.

The anode 32 or 42 may be made of useful materials that are generallyknown in the art. By way of example, an exemplary anode material forSOFC applications is a ceramic/metal mixture (“cermet”), with particularexamples including, but not limited to, yttria stabilizedzirconia/nickel, samaria doped ceria/nickel, samaria doped ceria/copper,and the like, composite mixtures of catalytically active, electricallyconducting, and ionic conducting ceramics can be considered as well. Thecathode 34 or 44 may also be made of materials that are known to beuseful in the art, with exemplary materials for SOFC applicationsincluding a composite mixture of an electrocatalyst and an oxygen ionconductor. Particular examples include, but are not limited to,lanthanum strontium maganite/yttria stabilized zirconia, lanthanumstrontium cobaltite ferrite/samaria doped ceria, samarium strontiumcobaltite/samaria doped ceria, and the like.

It will be appreciated that the present invention may be practiced usingelectrolytes and fuel cells of a variety of configurations and types.FIG. 6 illustrates an additional electrolyte embodiment shown generallyat 50. Two generally vertical cores 52 are on opposite sides of asubstrate 54. A plurality of projections 56 extends from opposite planarsides 60 and 62 of the cores 52. The substrate 54 is preferably anintegral portion of the electrolyte 50.

FIG. 7 illustrates an additional fuel cell embodiment of the inventiongenerally at 70 that includes the electrolyte 50. In the fuel cell 70,an anode 72 is attached to the core 52 and projections 56 on a firstside of the substrate 50, while a cathode 74 is attached to the core 52and projections 56 on the opposing second side of the substrate 50. Twoenclosures 76 and 78 are also provided for enclosing the cathode 72 andanode 74, respectively. As will be appreciated by those knowledgeable inthe art, the enclosures 76 and 78 may be used to contain fuel and/oroxidant gas for reaction with the anode 74 and/or cathode 72. Also,these enclosures 76 and 78 can contain porous anode 74 and cathode 72materials. The enclosures 76 and 78 may comprise any enclosure that aregenerally known to be useful in the art, including, by way of exampleand not limitation, manifolds, chambers formed by walls, and the like.

Those skilled in the art will appreciate that individual fuel cellsconsisting of a single electrolyte, single cathode, and single anode mayprovide a relatively small current and voltage that will not besufficient for many applications. For this and other reasons, individualfuel cells are often combined and electrically linked in series orparallel in order to provide a total current and voltage of a larger,more useful magnitude. Fuel cells of the present invention may beprovided in such configurations.

FIG. 8, for instance, illustrates a fuel cell assembly of the inventionshown generally at 100 that includes a plurality of individualelectrolytes shown generally at 10 consistent with the electrolyte 10 ofFIG. 1, and include a generally vertical core or core 12 supported on asubstrate 114. Pluralities of projections 16 extend from opposite sidesof each of the cores 12. An anode 132 is connected to one side of eachof the cores 12 and the plurality of projections 16 extending from thatside. A cathode 134 is connected to the opposite side of each of thecores 12 and to the plurality of projections 16 that extend from thatside. A manifold 136 is provided to cover the substrate 114, theelectrolytes 12, the pluralities of anodes 32, and the plurality ofcathodes 34.

The manifold 136 also serves to define a plurality of channels 138. Eachchannel 138 has at least one port (not illustrated) for communicatinggas to and from the channel. The anodes 132 and cathodes 134 arearranged such that each of the channels 138 contains only anodes 132 oronly cathodes 134. That is, the anodes 312 are arranged in adjacentpairs, and the cathodes are arranged in adjacent pairs. Put another way,the fuel cell assembly 100 has two anodes 132 connected to adjacent ofthe electrolytes 10 being adjacent to one another, and likewise with twocathodes 134 connected to adjacent of electrolytes 10 being adjacent toone another. Each of the individual electrolytes 10 with theirrespective connected anodes 132 and cathodes 134 may be electricallylinked by a current collector (not illustrated) in series or parallel.

It will be appreciated that many additional configurations ofelectrolytes and fuel cells of the present invention will also offeradvantages. The fuel cell assembly shown generally at 200 in FIG. 9, forexample, has a plurality of channels 238 that each have up to fouranodes 232 or cathodes 234 therein. The anodes 232 and cathodes 234 areconnected to opposing sides of electrolytes 10 that are consistent withthe electrolytes 10 of FIG. 1 and include a core as well as a pluralityof projections that extend from the core. As illustrated, the channels238 are defined by walls 240 that extend between the two opposingsubstrates 214, with some of the walls 240 received on electrolytes 10and the two end walls that are received on the substrates 214.

The anodes 232 and cathodes 234 are arranged so that each channel 238contains only anodes 232 or cathodes 234. Put another way, anodes 232are connected to the first side of a first electrolyte 10, and to thesecond side of the adjacent electrolyte 10 on each of the substrates 214so that the anodes 232 connected to sequential electrolytes 10 areadjacent to one another. Cathodes 234 are arranged in a similar manner,so that cathodes 234 from sequential electrolytes 10 on each substrate214 are adjacent to one another.

FIG. 10 illustrates still another fuel cell configuration of theinvention. The fuel cell shown generally at 300 comprises a substrate314 with a plurality of individual electrolyte formations 310 supportedon each of its top and bottom opposing sides. Each of the electrolyteformations 310 are consistent with the electrolytes 10 of FIG. 1 andinclude a core or core as well as a plurality of projections orprojections that extends from the core. The substrate 314 is made of thesame material as the electrolyte formations 310, and is preferablyintegrally connected thereto to form a part of the electrolyte.Accordingly, the electrolyte formations 310 on each of the opposingsides of the substrate 314 are electrically linked, and the formations310 and the substrate 314 collectively form a functional singleelectrolyte.

An anode 332 is connected to the plurality of electrolyte formations 310on one of the substrate's opposing sides, and a cathode 334 connected tothe plurality of formations 310 on the other of the opposing sides. Theanode 332 and cathode 334 thereby strongly anchored to the electrolyte314 through the plurality of formations 310. A manifold 336 is connectedto one side of the electrolyte substrate 314 to define a channel 338through which gas may be communicated using at least one port (notillustrated). It will be appreciated that an additional manifold couldbe provided to define a channel for containing the cathode 334. It willalso be appreciated that other fuel cell embodiments of the inventionmay include a plurality of fuel cells 300 that are electrically linkedto one another in series or parallel.

It will likewise be appreciated that other fuel cell and fuel cellassembly embodiments of the invention discussed herein may be combinedin series, parallel, or in other ways. For example, FIG. 11 illustratesa fuel cell assembly 400 that generally comprises two of the assemblies200 of FIG. 9 stacked on one another. A substrate 215 separates the twoassemblies 200 from one another, and supports electrolytes 110 on bothof its upper and lower sides. The substrate 215 may contain two of thesubstrates 214 layered on one another, or may be a single substratelayer. The anodes 232 and cathodes 234 from each of the cell assemblies200 may be linked in series or parallel to deliver a current thatrepresents a cumulative total from all of the assemblies 200. It will beappreciated that while only two fuel cell assemblies 200 have beenillustrated, any desired number of fuel cell assemblies 200 could bestacked. Such configurations offer the advantage of a relatively highpower output while requiring only a relatively small footprint.

In addition to electrolytes and fuel cells, the present invention isalso directed to methods for making an electrolyte, and to methods formaking fuel cells. FIG. 12 is a flowchart illustrating an embodiment ofa method of the invention for making an electrolyte of the invention. Inan initial step, a plurality of layers is deposited on a substrate, withat least two of the layers having different etch selectivity's (block402). The layers may be made of any of a variety of suitable materialsthat are generally known in the art, with examples including, but notlimited to, silicon, oxides of silicon, poly-silicon, doped silicon,spin on glass, etc. The layers may be deposited using deposition methodsgenerally known in the art, including but not limited to vapordeposition, sputtering, and the like. Preferably, the at least two ofthe layers that have different etch selectivity's are made of differentmaterials. It will be appreciated, however, that layers made of the samematerial may have different etch selectivity's. For example, two layersmade of the same material but having different particle sizes may havedifferent etch selectivity's.

A first chamber defining the electrolyte core is then defined in theplurality of layers through anisotropic etching of the layers (block404). Those skilled in the art will appreciate that other removalmethods in addition to etching are known for defining a chamber in thelayers and will be useful for practice of the invention. In defining thecore chamber, a portion of each of the two layers made of differentmaterials is removed. Preferably, a portion of each of the plurality oflayers is removed. An etching or other removal procedure is accordinglyused that is effective for operating on both of the two differentmaterials, or with each of the different etch selectivity's.

In a subsequent step, at least one additional chamber is defined from aportion of only one or more selected of the plurality of layers todefine at least one electrolyte projection (block 406). This step may beaccomplished by using an etching or other removal technique that onlyselected of the plurality of layers are responsive to, or by usingetching that some of the layers are more responsive to than others. Forexample, if two layers A and B each have different etch selectivity's,an etching technique may be used that will affect only layers made of B,or alternatively that will affect B at a higher rate than A so as toetch away substantially larger portions of B than of A. Preferably aplurality of projection chambers is formed.

After these steps of defining the core and projection chambers, apattern exists in the plurality of layers that defines the electrolyte.This electrolyte-defining chamber is then filled with electrolytematerial (block 408). Filling the pattern may be accomplished usingtechniques generally known in the art, such as vapor deposition,sputtering, and the like. Also, a variety of materials are appropriatefor use as the electrolyte material, with exemplary materials includingthe ceramics discussed with reference to electrolyte embodiments of theinvention.

The remaining portions of the plurality of layers are then removed toleave a freestanding electrolyte structure on the substrate (block 410).By way of example, the freestanding electrolyte built through the stepsof this method embodiment may be consistent with the electrolyte 10shown in FIG. 1. To make a fuel cell that incorporates the electrolyte,a subsequent step of forming an anode and a cathode on the electrolyteis performed (block 412). The anode is preferably formed on one side ofthe electrolyte structure and the cathode on the other with the twoseparated from one another. Each of the anode and the cathode preferablyare connected to a plurality of the projections extending from theelectrolyte core. An exemplary fuel cell built through these steps maybe generally consistent with the fuel cell 30 of FIG. 4.

Embodiments of the present invention directed to methods for makingelectrolytes and fuel cells of the invention may be further illustratedby consideration of FIGS. 13(a)-13(g). FIG. 13(a) illustrates aplurality of layers 502 that have been deposited on a substrate 504. Theplurality of layers 502 comprises at least two individual layers 506 and508 that have different etch selectivity's. That is, at least a firstlayer 506 has a first etch selectivity, and at least a second layer 508has a second etch selectivity. Preferably, the two layers 506 and 508are made of different materials from one another. The first and secondmaterials are preferably distinct from one another in their resistanceto a particular technique of removal, such as etching. Those skilled inthe art will appreciate that a wide variety of materials will besuitable as either the first or second material in practice of theinvention. For example, a first material may be silicon, which may bereadily removed through steps of an isotropic SF₆ etch, while a secondmaterial may be SiO₂, which is resistant to removal through an isotropicSF₆ etch.

After the plurality of layers 502 has been deposited, a portion of themare removed through etching or through other steps to form a chamber510, as is illustrated by FIG. 13(b). That is, a portion of each of thelayers 506 and 508 has been removed to form the chamber 510. The chamber510 will define the electrolyte core, and may thus be referred to as acore chamber. The removal of both layers may be achieved by a removalprocess that effects both layers, or may be achieved by a plurality ofremoval steps of one layer and then the next using different techniquesas may be required for the particular layer.

In a subsequent removal step, portions of only the layers 508 areremoved to form a plurality of projection chambers 512, as isillustrated by FIG. 13(c). The removal process for defining theseprojection chambers is preferably a technique that is not effective inremoving an appreciable amount of the layers 506. Each of the projectionchambers 512 will define one of the plurality of projections of theelectrolyte. It will be appreciated that in this second etching step,some small portion of the first layers 506 may be removed. The amountremoved, however, will be small in comparison to the portions of thelayers 508 removed. Preferably, substantially no portion of the layers506 is removed.

In combination, the chambers 510 and 512 define a pattern 514 for theelectrolyte consisting of the core and plurality of projections. Theelectrolyte may then be formed by filling this pattern 514 withelectrolyte material 516, as is illustrated by FIG. 13(d). Techniquessuch as vapor deposition, sputtering, and the like may be used to fillthe pattern. After the electrolyte material 516 has hardened in thepattern 514, the remaining portions of the layers 506 and 508 areremoved to leave the freestanding electrolyte 518 illustrated in FIG.13(e). It will be appreciated in consideration of FIG. 13 that othersteps may also be provided, such as for example forming a currentcollector, forming a structural connector, or the like.

Those skilled in the art will also appreciate that other methodembodiments of the invention may be practiced to create electrolytesand/or fuel cells in other configurations. By way of example, it will beapparent that embodiments of the method of the invention could bepracticed to create any of the electrolyte or fuel cell embodiments thathave been discussed herein and illustrated in FIGS. 1-11.

By way of particular example, FIG. 14 is useful in illustrating anadditional embodiment of a method of the invention that is useful formaking another electrolyte embodiment of the invention. In FIG. 14(a), aplurality of layers 602 has been deposited on a substrate 604. Theplurality of layers 602 are made up of a plurality of first layers 606having a first etch selectivity and a plurality of second layers 608having a second etch selectivity. Portions of both the layers 606 and608 are etched or otherwise removed to define a core chamber 610 asillustrated by FIG. 14(b). Portions of only the first layer material 606are removed in a subsequent step to define a plurality of projectionchambers 612, as illustrated in FIG. 14(c). The portions removed are ofdifferent sizes to create projections of different sizes.

The core and projection chambers 610 and 612, respectively, are thenfilled with electrolyte material 614, as illustrated in FIG. 14(d). InFIG. 14(e), an electrolyte substrate 616 is deposited on top of thefilled core chamber 610 and remaining portions of the uppermostplurality of layers 602. The electrolyte substrate 616 is preferably ofthe same chemical composition as the electrolyte material 610. FIG.14(f) shows the result of depositing an additional plurality of layers618 on top of the electrolyte substrate 616. Like the plurality oflayers 602, the additional plurality of layers 618 are made up of aplurality of the first layers 606 and a plurality of the second layers608. A second core chamber 620 is then defined in the plurality oflayers 618 by removing a portion of each of the first layers 606 and thesecond layers 608, as is illustrated by FIG. 14(g). As illustrated, thesecond core chamber 620 may be of a different size or geometry than thefirst core chamber 610.

A plurality of projection chambers 622 is then defined by removing onlyportions of the second layers 608 as shown by FIG. 14(h). The corechamber 618 and the projection chambers 622 are then filled withelectrolyte material 610 as illustrated by FIG. 14(i). Removal of theremaining portions of all of the first layers 606 and second layers 608from both the plurality of layers 618 and 602 leaves the electrolytestructure 624 shown in FIG. 14(j). It is noted that the electrolytestructure 624 has an upper side core 626 and lower side core 628 ofdifferent sizes on opposite sides of the substrate 616, and has upperside projections 630 and lower side projections 632 that are not ofuniform size. Preferably, the total surface area of the upper sideelectrolyte core 626 and projections 630 is substantially the same asthe total surface area of the lower side core 628 and projections 632.

FIG. 14(k) shows an anode 634 and a cathode 636 that have been attachedto the electrolyte cores 626 and 628 and projections 630 and 632respectively, to make a fuel cell. The anode 634 and cathode 636 areseparated from one another. Those skilled in the art will appreciatethat other generally known fuel cell components may additionally beprovided, including for example a current collector and one or moreenclosures for communicating gas to one or more of the anode 634 andcathode 636.

In still an additional method embodiment for forming an electrolyte coreof the invention, an electrolyte structure is formed on a substrate andthen etched to form an electrolyte structure having at least oneprojection. FIG. 15 is useful in illustrating this method. FIG. 15(a)shows an electrolyte structure 702 formed on a substrate 704, with thestructure 702 made up of a plurality of individual layers 706. At leasttwo of the layers 706 have different etch selectivity's. Thoseknowledgeable in the art will appreciate that etch selectivity's may becontrolled through a variety of means, with grain sizes and choice ofbinder being two examples. When the structure 712 is exposed to anetching process, the different etch selectivity's of the layers 716 willcause etching to proceed to a different extent on the different layers,with an exemplary result shown in FIG. 15(b) having a plurality ofprojections extending from the electrolyte core.

While specific embodiments of the present invention have been shown anddescribed, it should be understood that other modifications,substitutions and alternatives are apparent to one of ordinary skill inthe art. Such modifications, substitutions and alternatives can be madewithout departing from the spirit and scope of the invention, whichshould be determined from the appended claims. Various features of theinvention are set forth in the appended claims.

1. An electrolyte for use with a thin film fuel cell comprising: anelectrolyte core supported on a substrate; and at least one electrolyteprojection connected to said core and separated from said substrate. 2.An electrolyte for use with a thin film fuel cell as defined by claim 1wherein said at least one electrolyte projection comprises at least twoelectrolyte projections integrally connected to said core, the first ofsaid two electrolyte projections extending from a first side of saidfirst electrolyte portion and the second of said two electrolyteprojections extending from a second side of said electrolyte core.
 3. Anelectrolyte for use with a thin film fuel cell as defined by claim 1wherein said electrolyte core has a three dimensional generallyrectangular shape, and wherein said at least one electrolyte projectionhas a three dimensional generally rectangular shape.
 4. A thin film fuelcell comprising the electrolyte defined by claim 1, wherein said atleast one electrolyte projection comprises a plurality of electrolyteprojections, and further comprising: a cathode in contact with at leasta first one of said plurality of electrolyte projections and with atleast a first portion of said core; and an anode in contact with atleast a second one of said plurality of electrolyte projections and withat least a second portion of said core, said anode separated from saidcathode.
 5. A thin film fuel cell as defined by claim 4, wherein saidelectrolyte core has two opposing sides, said anode connected to a firstof said two opposing sides and said cathode connected to the second ofsaid two opposing sides.
 6. A thin film fuel cell as defined by claim 4wherein said cathode comprises a thin layer wherein a surface of saidcathode substantially matches the surface of said at least a firstelectrolyte projection, and wherein said anode comprises a thin layerwherein a surface of said anode substantially matches the surface ofsaid at least a second electrolyte projection.
 7. A thin film fuel cellas defined by claim 4 wherein: said at least a first one of saidplurality of electrolyte projections comprises at least two electrolyteprojections, a first gap defined between said at least two electrolyteprojections, said cathode substantially filling said first gap; and saidat least a second one of said plurality of electrolyte projectionscomprises at least two electrolyte projections, a second gap definedbetween said at least two electrolyte projections, said anodesubstantially filling said second gap.
 8. (canceled)
 9. A thin film fuelcell as defined by claim 4 wherein: said anode is made of aceramic/metal mixture selected from the group consisting of: yttriastabilized zirconia/nickel, samaria doped ceria/nickel, and samariadoped ceria/copper; and the cathode is made of a mixture of anelectrocatalyst and an oxygen ion conductor selected from the groupconsisting of lanthanum strontium maganite/yttria stabilized zirconia,lanthanum strontium cobaltite ferrite/samaria doped ceria, and samariumstrontium cobaltite/samaria doped ceria.
 10. An electrolyte for use witha thin film fuel cell as defined by claim 1 wherein said electrolytecore is one of a plurality of electrolyte cores supported on saidsubstrate, each of said plurality of electrolyte cores separated fromone another.
 11. An electrolyte for use with a thin film fuel cell asdefined by claim 10 wherein said plurality or electrolyte cores beingarranged to define a plurality of channels.
 12. A thin film fuel cellincluding the electrolyte defined by claim 11, and further comprising ananode and a cathode connected to each of said plurality of electrolytecores, said anodes and cathodes arranged wherein said anodes definechannel walls of every other of said plurality of channels, and saidcathodes define walls of interventing of said plurality of channels. 13.A thin film fuel cell as defined by claim 12 further comprising amanifold for covering said plurality of channels.
 14. An electrolyte foruse with a thin film fuel cell as defined by claim 10 wherein saidsubstrate comprises a first substrate, and further comprising a secondsubstrate opposing said first substrate, a plurality of electrolytecores connected to said second substrate and facing said firstsubstrate, each of said plurality of electrolyte cores having at leastone projection extending from said core and separated from said secondsubstrate.
 15. A thin film fuel cell including the electrolyte definedby claim 14 and further including a plurality of walls extend betweensaid first substrate and said second substrate to define a plurality ofchannels. 16-17. (canceled)
 18. An electrolyte for use with a thin filmfuel cell as defined by claim 10 wherein said plurality of electrolytecores is arranged non-linearly to cause an increase in gas flowturbulence.
 19. An electrolyte for use with a thin film fuel cell asdefined by claim 1 wherein said substrate has opposing first and secondsides, and wherein at least one of said electrolyte cores is supportedon each of said first and second sides. 20-22. (canceled)
 23. Anelectrolyte for use with a thin film fuel cell as defined by claim 1wherein said core and said at least one projection are made of a ceramicselected from the group of ceramics consisting of: yttria stabilizedzirconia, samaria doped ceria, gadolinia doped ceria, and lanthanumstrontium gallium maganite.
 24. An electrolyte for use with a thin filmfuel cell as defined by claim 1 wherein said core has a width betweenabout 1 and about 1000 microns and a height between about
 0. 25. Anelectrolyte for use with a thin film fuel cell as defined by claim 1wherein said core has a width of about 1 micron or less, and a heightbetween about 0.25 and about 5 microns, and wherein each of said atleast one projections has a width of between about 0.25 and about 5microns and a height of between about 1 and about 2 microns.
 26. Anelectrolyte for use with a thin film fuel cell as defined by claim 1wherein said at least one projection comprises a plurality ofprojections and wherein at least some of said plurality of projectionsare of different sizes from one another. 27-45. (canceled)